How severe is CVE-2021-31403?

CVE-2021-31403 has a CVSS 3.x base score of 4.0, rated medium severity. It is exploitable over local access with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-31403 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-31403?

CVE-2021-31403 affects Vaadin. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-31403?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-31403 published?

CVE-2021-31403 was published on 2021-04-23 and last updated on 2026-06-17.

CVE-2021-31403

CVE-2021-31403 is a medium-severity vulnerability in Vaadin with a CVSS 3.x base score of 4.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-203.

Key facts

Severity: Medium (CVSS 3.x base score 4.0)
CVSS v2: 1.9
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-203
Affected product: Vaadin
Published: 2021-04-23
Last modified: 2026-06-17

Description

Non-constant-time comparison of CSRF tokens in UIDL request handler in com.vaadin:vaadin-server versions 7.0.0 through 7.7.23 (Vaadin 7.0.0 through 7.7.23), and 8.0.0 through 8.12.2 (Vaadin 8.0.0 through 8.12.2) allows attacker to guess a security token via timing attack

Frequently asked questions

What is CVE-2021-31403?: Non-constant-time comparison of CSRF tokens in UIDL request handler in com.vaadin:vaadin-server versions 7.0.0 through 7.7.23 (Vaadin 7.0.0 through 7.7.23), and 8.0.0 through 8.12.2 (Vaadin 8.0.0 through 8.12.2) allows attacker to guess a security token via timing attack
How severe is CVE-2021-31403?: CVE-2021-31403 has a CVSS 3.x base score of 4.0, rated medium severity. It is exploitable over local access with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-31403 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-31403?: CVE-2021-31403 affects Vaadin. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-31403?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-31403 published?: CVE-2021-31403 was published on 2021-04-23 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:vaadin:vaadin:*:*:*:*:*:*:*:*

More vulnerabilities in Vaadin

CVE-2021-31407 — High (CVSS 8.6): Vulnerability in OSGi integration in com.vaadin:flow-server versions 1.2.0 through 2.4.7 (Vaadin 12.0.0 through…
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CVE-2021-31405 — High (CVSS 7.5): Unsafe validation RegEx in EmailField component in com.vaadin:vaadin-text-field-flow versions 2.0.4 through 2.3.2…
CVE-2020-36320 — High (CVSS 7.5): Unsafe validation RegEx in EmailValidator class in com.vaadin:vaadin-server versions 7.0.0 through 7.7.21 (Vaadin 7.0.0…
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